Ultrahigh-frequency generator



Jan. 20, 1953 J. E. GIBSON ULTRAHIGH-FREQUENCY GENERATOR 4 Sheets-Sheet 1 Filed Oct. 25. 1945 3mm JOHN E. G|BSON Q H L N wmnh 25 mm woOIP O I Jan. 20, 1953 J. E. GIBSON ULTRAHIGH-FREQUENCY GENERATOR 4 Sheets-Sheet 2 Filed Oct. 25, 1945 mwm JOHN E.' GIBSON Jan. 20, 1953 J. E. GIBSON 2 ULTRAHIGH-FREQUENCY GENERATOR Filed Oct. 25, 1945 4 Sheets-Sheet s :E-LEZE:

grvuamm JOHN 'E. G\BSON Jan. 20, 1953 J. E. GIBSON ULTRAHIGI-I-FREQUENCY GENERATOR 4 Sheets-Sheet 4 Filed Oct. 25, 1945 Jwucnron 'JOHN E. GIBSON Patented Jan. 20, 1953 UNITED STATES PATENT OFFICE (Granted under Title 35, U. S. 'Code-(19'52),

sec. 266) 29 Claims.

This invention relates in general to high frequency energy apparatus and in particular to apparatus for the generation and amplification of energy in the centimeter wave region of the frequency spectrum.

There has been provided by prior art a species of triodevacuum tubes for negative grid operation according to conventional principles, but of unusual functional design. This design is such as to overcome to a large extent the upper frequency limitations of interelectrode and lead reactance efiects-and electron transit time effects. This design is also such as to lend itself readily to use as the component part of a system in which the various circuit elements are electrically long in that one or more of their dimensions represent an appreciable fraction of a wavelength at the frequency at which the system operates. By virtue of their peculiarconfiguration, thesetubes have inherited the appellations lighthouse tube, cartridge tube, and oilcan tube. these tubes, namel the lighthouse tube, the electron emitting cathode, the control grid and the anode which comprise the trio electrodes all are projected from the tube envelope in the form of annular contact rings at different parallel planes normal to the longitudinal axis of the tube. Each contact ring is separated from the other by a cylindrical piece of insulation, preferably glass, of progressively smaller diameters arranged in a stepwise fashion so that the oathode contains the largest ring, the anode the smallest, and the control grid the intermediate ring. While this stepwise arrangement is particularly adaptable for use with concentric lines as resonant elements in an amplifier or oscillator,

the power output of such a combination has heretofore been so low as to limit narrowly its use and particularly its useas a transmitter oscillator coupled directly toan antenna.

It is an object of this invention to provide high-frequency apparatus employing triode vacuum tubes in negative grid push-pull operation capable of usable power output in the microwave region of the frequency spectrum.

It is another object of this invention to'provide In one of 2. prises a sinusoidal oscillation .of extreme purity.

It is another object-of'this invention to provide vamicro-wave oscillator which can beefiectively amplitude modulated at audio or video frequencies without serious. disturbance of the natural oscillator or carrier frequency, and without incurring appreciable frequency modulation.

It is another objectof this invention to provide a micro-wave oscillator capable of simple mechanical tuning over a wide range of frequencies.

It is another object of T this invention to provide a micro-wave'oscillator which, in the same system, renders it possible to transmit either continuous wave or pulse type signals.

It is another objector thisinvention to provide a micro-wave oscillator which, in the presence of external vibration or power supply voltage variation, is capable of maintaining. a stable frequency and a constant output amplitude It is another object of this invention to provide a micro-wave oscillator in which twotriodes are so disposed with respect to resonant sections of concentricv line as to result in push-pull. operation with an attendant increase in power with respect to a single tube oscillator, and as to result in an advantageous circuit design which permits eflicient operation over a greater range of 'frequency than that conveniently obtainedwith a single tube triode oscillator. 7

It is another object of this invention toiprovide a compact, stable generator of high. frequency energy of .sufiiciently high power output and low voltage power'supply requirements to render it highly useful'in field or portable sysems.

It is'still another object of 'this'invention to provide a microwave push pull tri'ode. oscillator having such physical design as to permit the continuous circulation of a liquid coolant soas to extend the safe limit of 'plate power'dissipation and thereby thepower output ;of,the oscila or.

Other objects and features of this invention will-become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawings in'w-hich:

Fig. 1 is an idealized cross'sectionaldiagram of one embodiment of this invention;

Fig. 1a is a second view of'the'embodiment illustrated in Fig. 1.

Fig. 2 is a diagram, partly in cross sectionof a practical'embodiment of this invention;

Fig. 2a is a second view of the'embodiment illustratedin Fig.2}-

Fig. 2b is a detail view, partly in cross section, of the embodiment illustrated in Fig. 2;

Fig. 2c is another detail View of the embodiment illustrated in Fig. 2;

Fig. 3 is another detail view of the embodiment illustrated in Fig. 2; and

Fig. 4 is a diagram, partly in cross section of a variant practical embodiment of this invention.

Reference is now had in particular to Fig. 1 wherein there is shown, in idealized form, partly in cross section, an oscillator constructed so as to embody certain of the teachings of this invention. This embodiment comprises two electron discharge devices I and 2, hereinafter referred to as lighthouse tubes I and 2, or simply as tubes I and 2, mounted on a common axis with their respective anodes 3 and 4 facing each other.

Conducting metallic cylinder 5 is disposed in conducting electrical contact with anodes 3 and I in such a manner that its longitudinal axis coincides with the common axis of lighthouse tubes I and 2.

Concentric with cylinder 5 is conducting metallic cylinder 6. The ends of cylinder 6 are partially closed by integral annular metallic conducting elements I and 8. Through the central openings of annular elements 7 and B extend the anode sections of lighthouse tubes I and 2 in such a manner that the respective grid contact rings 9 and I are caused to abut elements 1 and 8. The third conducting cylindrical member It is also concentric with cylinder and has three cylindrical constituents the principal one of which forms the surface which, in general, bounds the oscillator circumferentially. The other two cylindrical constituents I2 and i3 serve, in general, to enclose the bases of tubes I and 2. Cylinders I2 and I3 are joined to the outer cylinder of II by means of integral annular metallic conducting elements I4 and I5 while the free ends of both cylinder I2 and cylinder I3 are partially closed by integral annular metallic conducting elements I6 and H which provide abutting surfaces for cathode contact surfaces I8 and I9.

Neglecting the anode to grid interelectrode capacitances of tubes I and 2, cylinders 5 and 5 together with those portions of anode and grid of tubes I and 2 lying within the tube envelopes will be seen to form the elements of an openended concentric transmission line, inasmuch as the two are coaxially disposed so as to act as conductors for the axial flow of current. As is known last mentioned resonance condition is the one at which the particular embodiment of Fig. 1 is most readily operated at frequencies of approximately 3000 megacycles per second. While there is an infinite number of high r frequencies for which the line itself is resonant, each determined by the number of half wavelengths included in the line length, they are of little importance in .this invention when designed for the 3000 megacycle frequency band inasmuch as they generally transcend the region of the spectrum in which the interelectrode spacing of tubes I and 2 do not introduce transit time difficulties too great for a sensible power output. The grid-to-plate capacitance of tubes I and 2 connected across each end of the line has the effect of increasing the electrical length of each half of the line by an amount which is less than one-quarter of the wavelength at any frequency. For this reason, the line itself has been made so as to have a physical length somewhat shorter than that required by strictly electrical length calculations for the desired frequency.

In a somewhat more complicated manner, constituents 6, I, 8, II, I2, I3, I4, I5, I6, and IT, together with those portions of cathode and grid electrodes of tubes I and 2 lying within the tube envelope, comprise in effect another open-ended concentric transmission line having its terminals at each end at cathode and grid of tubes I and 2 respectively. Of these constituents, element 6 and that portion of element II immediately surrounding and having a length roughly equal to element 6 will be seen to comprise a conventional concentric line. Elements 1 and It at one end and elements 8 and I! at the other end, taken together with those portions of the grids and cathodes lying within the envelopes of the respective tubes I and 2, comprise two radial transmission lines which diiier from concentric transmission lines as a class chiefly in that in general the electric field is longitudinal, the magnetic field is circumferential, and the current flows radially toward and from the center. These radial cavities, together with the forementioned concentric line section formed by elements 6 and I I, constitute the basic line sections necessary to form a transmission line terminating at grid and cathode terminals of the respective tubes, for it is necessary only to extend the diameter of elements i6 and IT to permit these elements to join element II in order to form a continuous transmission line extending between corresponding terminals of tubes I and 2. The single transmission line so formed will possess a plurality of resonant frequencies in the manner described in connection with the concentric line composed of elements 5 and 6, and the electrical length of the line will be greater than the physical length as measured between elements It and I? by an amount determined by the electrical length of line represented by the radial cavities from the terminals at cathode and grid to the locus of the points of connection to the common central line section. The physical dimensions of the elements 6, I and 8 comprising the effective inner conductor of this transmission line are governed at the minimum values by the dimensions these elements assume for operation of the concentric line composed of elements 5 and 6 in a particular mode at a particular frequency. For these reasons the electrical length of the line containing elements 6 and I I will generally equal or exceed the electrical length of the concentric line containing elements 5 and 6. Also in general the electrical lengths of these primary lines will differ sufficiently with respect to one another to require that means be provided to change the electrical length of one in such an amount as to permit optimum operation of the system as a whole. Such a change is most readily provided in the outer line, and the direction of the change in electrical length may be in such a sense as to operate the line at either the next higher or the next lower number of half wavelengths permitting push pull operation. The means chosen to effect this change of electrical length while retaininga constant physicali length .may be Jan-y one-of 'anumber of -methods.

symmetrically disposed with respect to the :line

midpoint. .Thevariable capacitancesintroduced across the lineby these plugs permit increasing the-electrical.length of the line to the optimum value. Another method of attainingthie same objective consists of the. introduction of movable conducting rings suspended .in the line. in :a T0011- centric; relation with cylinder 6, separated from cylinders 6 and I i, and symmetrically. disposed withztrespect-to .theline midpoint; Symmetri+ cally varying the positions alongthe line occupied by. these rings cpermits the :capacitancess...across .thjelline 'due: to: the .rings :to 2 be moved toward .or away fromgpointsirepresenting::voltage.iloops at .thedesired ifrequency,z.and hence permits the capacitances provided by .therings to exertra var rlable lengtheningxof jtheline; Athird and-gpreferred methodoi introducing a change. inthe electricalxlength of the line is that shown in-Fig. 1, :whichxconsists-of providing reentrant concentric line sections at each end, atone end composed 'of elements; Ml, andthe portion of element l l immediately surrounding element 12, and at the other end composed of elements 3, l 5, and the portion of-element l I immediately surround-- .ing element :3. The open terminals of these line sections .are connected to element 56 and to :one end of the middle portion of element l l in the case of the linesection containingelements l2 and l l, and to :element H and to the correspondingrend of the middle portion of element 1 l in the case of the line section containing elements l3 and Eli. Thus theimpedances looking into the terminals of these line sections are symmetrically connected in-series with the-effective outer conductor of the line at more or less Well-defined points distant from the line midpoint by amounts ap-. proximately equal to half the length of element 6. .It will be recognized bythose versed in vthe art thatthe impedance oitheline sectioncontaining elements l2za-nd Hi, andsimilarly the impedance of its counterpart at the opposite end, is a function of its length, and itwi'll be recognized also that-the insertion of an impedance other than zero in series with one of the conductors of a transmission line causes a change in the effective length of the line. Thus it will be seen thatithe length of the line sections so connected inseries with the -effec-tive-outer conductor of the line extending between tube terminals may be chosen to efiect a vchangeinelectrical length of the line a whole. The principles underlying the application of this tuningmeans will be described :more fully later in connection with a-specificembodiment of this invention.

Referring to the plate-grid line composed of elements 5 and E, it will be recognized that for those frequencies of resonance for which the electrical line length is on odd multiple of one half wavelength, a voltage node exists across the line at the midpoint, and the polarities of the voltages existing at the ends of the line are opposite. This 180 degree phase difierence between the voltages at the tube terminals leads to the designation of operation corresponding toone of these resonant lengths of line as push-pull operation. On the other hand, forthose frequencies of resonance for which the electrical length of 'theplate-grid line is an even multiple of one half wavelength, a voltagegenerallyother than zero; exists'racross; the. line midpoint," and the polarities :of, the voltages at the ends of the line are the same, i. e., the tubes are operatediin phase; Operation in the-latterconditioniisless desirable thanin theformer pushspull condition, for :reasons of preventing the loss .ofjpower through radiation on theexternal leads; In the same manner; push-:pull operation requiresxthat the electrical length of the cathode-grid linebe substantially an oddmultiple of one half wavelength, and operation of this line with. such ,an electrical length yields avoltage :node across ,its midpoint as in the case of. the plate-grid line.

The .circuit system. consisting :of the tubes and the two .tuned lines will be recognizedas constituting the essential elements ota .push.-,pull tuned-plate tuned-cathode.oscillator, foryif .Tthe plate-grid .line is tuned to. present the proper value oi inductive impedance between plate and grid terminalsxand if the cathode=grid:circuitis tuned .to. present theiproper value of capacitive impedance between cathode and grid terminals, the system may oscillate-with the plate-cathode inter-electrode tube capacitances serving as 'feed back coupling. For-the values of plate-cathode capacitance inherent within the tubes proper operation is not generally obtained and it is usually desirable to. provide additional feedback coupling meanswithin the circuit system.

If an instant of time be chosen'suc'h that the voltage of anode=3 with respect to grid 9 of tube is at a positive maximum, the voltage of anode d with respect 'togrid. IQ of tube :2 will be at a negative maximum. .If at the same time there be suitable coupling between the two resonant sections, the voltagezoi cathode is with respect to grid 9 of tube l willalso beat apcsitive maxi mum While the voltage associated with the cor-.- responding electrodes of tube 2will be at a nega tive maximum. Thesecondi-tions will be recognized as those requisiteto amplification orselfoscillation. The preferred method of establishing suchconditions in an oscillator constructed according to the teachings of this invention for frequencies approximating 3000 megacyclesis by means of coupling slot 22. Thisslot, of a length electrically approximating a half wavelength at the-frequency of oscillation, functions as a common impedance between the two resonant sec-, tions and thereby provides energy transfer from the plate grid section to the cathode-grid section for feedback. couplingof the proper phase in a manner described in mycopending application S. N. 624,619 entitled Microwave Slot Coupl'mg filed October 25, 1945. It should. bepointed out herethat, as is well known, there will beno coupling between the resonant sections merely by virtue of their common use of cylinder 5 since, at the frequencies under consideration, current flow is substantially a surface phenomenon and the thickness of cylinder 8 is very large in comparison to the depth of current penetration. Further, the capacitance which exists between cathode and plate of each tube, while introducingcoupling of the proper-sense to excite self-oscillation is generally of insufhcient magnitude to support such oscillation.

If both of the tuned lines of the oscillator were essentially equal in electrical length, the energy fed back by coupling slot 22 would be out of phase with that required for proper oscillatory phase relations at the tube ends of the lines. The cathode grid line,.therefore, is made one half wavelength electrically longer than. the plate-gridline on .each sideoi the mid.-

point so that a 180 phase change occurs which provides the positive feedback relations necessary for oscillation.

This particular choice of energy feedback means dictated a choice of relations between the electrical lengths of the plate-grid section and the cathode-grid section which, for frequencies of about 3000 megacycles, is most conveniently that of three half wavelengths and five half wavelengths respectively but which is not necessarily limited to these specific values. Had convenience of construction and accuracy of tuning not influenced the choice, the plate-grid section could have been a single half wavelength and the cathode-grid section three half wavelengths without disturbing the phase relations at the midpoint and end points of the oscillator. In the general case, the choice of feedback means made in Fig. l, or, for that matter, any feedback means chosen which requires a similar phase relationship between the two resonant sections at the oscillator midpoint, requires only that the two sections each be an odd integral number of wavelengths long electrically and that they differ in electrical length by an odd integral number of full wavelengths. This flexibility can be extended further by the use of optional feedback methods such as capacitive coupling in parallel with the plate-cathode capacitance of each of the tubes in which case the midpoint phase is immaterial as long as the midpoint remains a voltage node point for both sections and the electrical length relations can therefore be extended so as to include differences of zero and both odd and even integral complete wavelengths. If the vacuum tube exciting means be chosen such as to have the proper amount of cathode-to-anode capacitance for feedback coupling, this inherent feature can constitute the means of energy transfer.

To those versed in the art, it will be apparent that, were the vacuum tube exciting means chosen so as to provide insufiicient feedback to support self-oscillation and no added feedback means were provided, the apparatus of Fig. 1 may be provided with a means of feeding energy into the grid-cathode resonant section and would function as an amplifier. Since both the gridanode and grid-cathode circuits are resonant sections, 1. e., tuned circuits, the amplifier would be selective and provide maximum power output at the resonant frequency of the output circuits.

The higher energy level existing in the plategrid line establishes it as the logical sink for oscillator energy output. For this reason, an output coupling loop 23 is inserted into the annular space between cylinders 5 and 8. The energy induced in the loop is transmitted to the point of use by means of a coaxial line 24. It will be noted that this loop is located at the midpoint of the resonant section which is the location of a voltage node and hence a current loop. The field which exists by virtue of this current maximum is disposed circumferentially in the usual manner of concentric line operation so that orientation of the loop as shown in Fig. 1 results in the maximum degree of coupling. The output is reduced by rotation of the loop away from the longitudinal plane. It will be seen that this inductive loop type output coupling is convenient by virtue of its midpoint location. It will also be seen that other types of coupling, as suit the requirements of a particular situation, may be employed. For example, if it is desired to transmit the oscillator output to an antenna by means of a waveguide, a midpoint aperture forming a common impedance between the cathode-grid resonant section and the waveguide is an alternative means of coupling although, in general, the higher energy level in the plate-grid section makes it the logical output sink. Capacitive output coupling may also be used provided proper locations are chosen (points of voltage loops) and care is exercised to avoid unbalancing the electrical symmetry.

Inasmuch as the midpoint of the sections is a voltage node for both sections, it represents an ideal location for plate and grid D.-C. connections. Connections placed at such a midpoint location have a minimum effect on operation in the desired mode since it represents a point of voltage minimum at all frequencies. The B+ supply is therefore introduced into the oscillator by means of lead 20 through openings and 26 and connected to cylinder 5 at point 21 as shown in Fig. 1a and grid lead 3| is introduced through opening 28 and connected to point 29 on cylinder 6. Lead 2| is returned through common resistor 30 to cathode-pins 3| and 32 in parallel to complete the cathode grid D.-C. circuit. Heater voltage connections, not shown, are made to pins 33 and 34 of tube and to pins 35 and 36 of tube 2.

It is recognized that the idealized oscillator of Fig. 1 is not tunable in the form shown and that certain necessary structural details have been omitted. For this reason reference is now had to Fig. 2 in which is shown a practical embodiment constructed according to the teachings of this invention, and designed for the frequency range from 2400 to 3400 megacycles.

The principles of operation are the same as those outlined with respect to the oscillator of Fig. 1 but mechanism providing for tunability has been added, circulatory cooling means has been added and practical considerations have dictated certain changes in construction. The general disposition of components is the same so that there is again virtual symmetry around the physical transverse midpoint. This virtual symmetry permits the description of either end of the oscillator, it being understood that the other end is essentially identical.

Tube 5|, which is representative of tube 2 in Fig. 1, may be removed by unscrewing two studs only one of which, 52, is shown in this elevation view, and withdrawing cylinder 54. The latter contains an annular portion which engages annular recess 56 of tube socket I I2 to thereby provide firm support and coaxial alignment of tube 5| when cylinder 54 is locked in place. For explanation of the construction and operation which follows immediately, reference is had to Fig. 2b which is an enlarged sectional view of the oscillator of Fig. 2 confined to the general region of tube 5| and the midpoint of the oscillator.

As tube 5| is pressed into place, anode 5T nests inside dual cylinder 58 which is so constructed of tempered brass and slotted as to provide an effective multi-finger electrical and thermal contact with anode 51. In the annular space between the dual elements of cylinder 58 and concentric therewith is cylinder 59 in a telescopic arrangement which permits the longitudinal movement of cylinder 58 with respect to cylinder 59. The outer element of cylinder 58, including raised portion 58a, is slotted and beaded at the end opposite to that accommodating anode 51 and is of spring quality material so as to provide an efaccepts fective multi-"finger electrical contact with cylin der' 59. Cylinders '58 and 59 -'constitute the essential parts of the plate cylinder and correspond tocylinder fi-ofFig. 1. Asanode 5'! is pushed home in'cylinderBS; grid contact ring lit presses against radially slotted annularring ti to provide electrical continuitybetween' ring 6t and dual cylinder 62'. dual elements of cylinder 62 and concentric therewith-is cylinder 63 ina telescopic arrangement which permits the longitudinal movement of cylinder 62 with respect to cylinder -63. Both the innerand outer elements of cylinder 82ersslotted at the end which constitutes the point of entry of cylinder 63- andare-constr-uctedof spring qualitymaterial toprovide-good high frequency contact. The fingersformed bythis slotting are provided'with raised'bea'd like contacts'atsaid-- point of entry so that electrical continuity with cylinder 63 at said point is assured regardless oi the position of that cylinder within cylinder 62. Cylinder 62' and 63 constitutethe cssential parts of thegrid cylinder and correspond to cylinder 6 oil-Fig. 1. Coincidental with the making of'con tact --by rings fifi and- Si or the grid circuit; cathode contact 'surfacefit presses against radially slotted annularring 65t0 provide'electrical continuity between surfacefi l andcyli'nd'cr t6. Concentric withand surrounding cylindertt iscylinder 67 which, in general, constitutes the circumferential boundary of the oscillatorproperat-this point. Intothe annular space between cylinder-s litend longitudinally. The freeends of dual cylinder 68 are slotted, beaded, and of -spring quality ma-- terial so as to-provide-efiective multi-fingerhlgh frequency contacts with cylinders 66 andtl-at such free ends regardless of thelongitudinalposi tion of dual cylinder 68. Assembled'with cylinder 61* and held in fixed relation thereto by retainer ring 69 is cylinder-1E! so as to form an extension of cylinder 61. lhe freecndof cylinder this also provided with spring quality slotted and beaded construction so as to provide proper contact with enclosing cylinder l I at such end. Cylinder'lfl lsfree to'move longitudinally with re spect' to cyli'nder H independently of any move-'- The assembly 1 commentor dual cylinder 68': prisingcylinder 61-, cylinder i l and cylinderll corresponds to cylinder H of Fig. l. correspondsto element l 's'of Fig. 1; cylinder-t6 correspondstoelement [3, and dual cylinder 6'8 correspond to element l5.

The evolution from the idealized constructionof Fig. I to the practical construction of Fig. while it resulted in no essential difference in-the' mode of operation, introduced certain endeffects and discontinuities in characteristic impedances which had the effect of requiring a reduction in the physical 'lengthsoi the plate-grid resonant section and the cathode grid resonantsecti'on in 7 order to maintain equivalent electrical lengths. It is this phenomenonwhi'oh-would have resulted iii-physical lengths too short'to be practicalhad an attemptbeen madetooperate'the plate-grid line at itslowest resonant frequency, 1. e., witha physical length such as to yield-an electrical length of only one-half wavelength rather-than, in accordance with the teachings of this invention, with a physical length such asto yield'an' electrical length of three half wavelengths; A corresponding difiiculty would have resulted in connection with the cathode-grid line had anattemptbeen made tooperate it in a lower frequency mode. Another important result of this- In the-annularspace between the Ring '65 l extended construction is that it "renders-Hess" critical the adjustment'of physical line lengths during tuning of the oscillator. With further reference to Fig. 2b, the movable'elernents of'the.

plate cylinder assembly, 'the grid cylinder assembly and the cathode cylinder assemblyl'not including dual cylinder 68 are held fixed inrela--' tion to each other by dielectric annularrings =12! and 13 so that they may move jointly alongi-the common axis, of the oscillator; Rings l2 and-13;

not only provide for this. joint movement but-"also act as supports andpreserve the concentric relae tionship. of themovable cylinder elements.

In'F-ig. 2,:outer cylinder 'H'is. shown to'be held; fixedin position with respecttto chassis 14 and: supported by four lugs, only two: of which; 15.-

and 16', are shown. In Fig. 2b,-cylindrical cle"-.

ment 63 0f the. grid cylinder-assembly is heldfixed' in position with respect tovthe chassis by annular.

dielectric rings 'TSSandtil. The fixedaposition ofr cylindrical element 59 of: the plate cylinder as-' sembly relativeto the; chassis is maintained. by: and. annular dielectric:

tubular element 8| ring'tz.v

Certain of; the: advantagesof a push-pullv 0801].?

lator constructed: according touthe teachin'gsiofr this invention. over a single:tube=oscillatorsoomr prising; a lighthouselorrsimilan tube arrdrconcentriov line resonant sections come about: as aresulti of circuit design. considerations.

planation', ,inzmicrowave triode oscillatoricircuits; functioning in a conventional negative ..-Ig1id.l

By way' ofrexe triode manner, thecircuit conductors that "are attached to. thezgrid andzplateare operated at::a.- potential negative. andpositive respectively'with resp'ectto the catliodeaor ground potential. Itsis.

therefore necessary to provide. Dr-C. insulation. between. the; portions of thetunedr circuits having different potentials; andalso it is necessary to provide R-.-F. by-passing. at. the: points: of separa.-

tion of those. portions "of thecircuit QperatedJat potential differences. in order to. complete the R.-F circuits and. avoid thezcoupling. of.-R-; -F..

fact. that the by-pass-elem'ent fu'nctionn also as-;;a

choke. These techniques-are readily applied in; narrow band oscillators; butsbecome. awkwardior wide, band. applications since. any byepassnlement, mica condenser orzline section, assumes;.the:pron-.- ertiessof' Rr-F. transmission lines. at i centimeter wavelengths andiisrela-tively criticalewith-respect to the frequency range over which it is effective;

Therefore, wide band single? tube oscillator: circuits, particularly-for zpulsedsoperation, are? difiie cult to-design-in such a manner asrtoxobtain optimum overaliperformance togetherwith com pact, straight-forward construction;

These. design problems are avoided wby. the teachings-Jot this invention. by providing -Dl-(l; connections to thecplate and grid conductors at circuit midpoints where the tendency to couple R.-F. energy to externalleads is at zip-minimum (voltagenode) Sincethecircuit is symmetrical i about the midpoint, this teaching applicable without.regard-to frequencyrangecovered .by tlie" acaaase oscillator. Thereby is avoided also the introduction of lumped capacitances which are objectionable from the standpoint of modulated or pulsed operation.

- In Fig. 2, the B+ supply connection is made to the plate cylinder assembly by means of tubular element 8| which is in electrical contact with hose connection 83 but is insulated from cylinder II by ring 82 and from cylinder E3 by an air gap. The D.-C. connection to the grid cylinder is by means of binding post assembly 84 which is insulated from cylinder 'II by means of dielectric washer 85. A resistance of approximately 5000 ohms (not shown) is connected to this binding post and has its opposite terminal run to the cathode connections in the bases of the two oscillator tubes so as to complete the D.-C. grid cathode circuit in a manner similar to that described in Fig. 1. Tendencies toward intermittent operation (motorboating) due to too large a time constant grid resistor-grid capacitance combination are minimized by the fact that the capacitance from grid cylinder to ground is kept small by avoiding mica by-pass capacitances or other lumped capacitances in the grid cylinder circuit construction. Since the grid resistor is common to both tubes, half the resistance is required that would be needed to obtain equivalent bias relations for a single tube. Heater voltage connections are made to the appropriate pins of tube socket H2 as described in connection with Fig. 1.

Energy to support oscillation is transferred from the grid-anode section to the grid-cathode section by means best illustrated by Fig. 2c in which transverse circumferential coupling slot 63a is disposed at the midpoint of cylindrical member 63. In accordance with the teachings of copending application supra, the physical length of slot 63a is less than that required by an unmodified construction while at the same time its electrical length is maintained by means of lumped capacitance across the slot midpoint. A portion of this capacitance consists of two raised conducting elements 8'! and 81a one on each edge of slot 63a at its midpoint so that the two oppose each other across the slot opening. In Fig. 2a raised element 81 is visible, it being understood that identical element 81a is located across the slot therefrom and is hidden thereby in this view. The other portion of this lumped capacitance is movable and consists of plate 88. It willbe seen that the total capacitance provided by plate 88 across the slot is the series sum of the capacitance from each side of the slot to the portion of plate 88.immediately adjacent and that movement of plate 88 can be utilized to vary this capacitance and thereby the electrical length of the slot to the optimum value for coupling between the two resonant sections. Threaded adjusting member 89 is supported from outer cylinder II by means of boss 90.

In the embodiment of Fig. 2, as in the embodiment of Fig. 1, energy is coupled to an external load by means disposed in the plate-grid resonant section. This means is represented in Fig. 2a by inductive coupling loop 86. This coupling loop 86 is positioned by connector 80A which provides for the connection at 8013 of a conventional coaxial transmission line (not shown) for energy transfer purposes.

Since the electrical lengths of the plate-grid resonant line and the cathode grid resonant line determine the frequency of operation, tuning is accomplished by variation in the physical lengths 12 of the resonant sections. operated in the same mode, i. e., both at the same number of integral half wave lengths, and their end conditions and characteristic impedance irregularities were the same, tuning to a higher or lower frequency would be simple since it would only involve shortening or lengthening the resonant sections the same amount. Feedback relations have, however, dictated the use of an equivalent three half wavelength plate grid line and an equivalent five half wavelength cathode-grid line in this embodiment. It follows therefore that a change in physical length of the plate-grid line amounting to a 5% electrical change corresponds to only about a 3% electrical change in the cathode grid line. This condition requires differential physical changes in the tuning of the two resonant sections. In the oscillator of Fig. 2 this is accomplished by means of dual cylinder 68 in a manner which is described in the following paragraphs.

Longitudinal movement imparted to cylinder 61 will, by virtue of the construction hereinbefore described, cause the same physical length changes in both of the resonant sections. This movement alone will tune the two sections to two different frequencies and is accomplished by means of rotatable threaded shaft 9I and lug 92 into which it is threaded. Lug 92 is securely attached to the assembly which includes cylinder 6! so that rotation of shaft 9| is translated into longitudinal movement of that cylinder. This mechanism, together with that which results in compensating movement of dual cylinder 68, may best be seen in Fig. 3 and reference is now had to the plan view of the tuning arrangement illustrated in that figure. Lug 92 appears in cross-section threadably engaged with shaft 9I. Longitudinal movement of lug 92 is accompanied by a similar movement of threaded sleeve I20 through the agency of thrust lug I2I. Threaded sleeve I20 is free to rotate with respect to thrust lug I2I but moves longitudinally as lug I2I moves. Such longitudinal movement is translated to cylinder 68 through the agency of lug assembly I22 threaded over sleeve I20 and an upright member attached to lug assembly I22 similar to upright member 94 shown at the opposite end of the oscillator in Fig. 2. Keeping in mind that the oscillator is substantially symmetrical about its midpoint, it will be understood that the upright memher which causes cylinder 68 to move does so through a slot in the wall of cylinder 87 similar ment required to change the position of cylinder 68 with respect to cylinder 01 as the oscillator is tuned is accomplished by means of shaft 93 which passes coaxially through sleeve I20. Shaft 93 is free to move longitudinally with respect to sleeve I20 but is keyed to sleeve I20 in such a manner that they have a common rotational movement. Keying slot I23 in sleeve I20 provides this selective relationship such that shaft 93 is capable of causing sleeve I20 to rotate simultaneously with the longitudinal movement of sleeve I 20 imparted by rotation of shaft 9 I. Rotation of shaft 93, and hence of sleeve I20 causes the longitudinal movement of lug assembly I22 which is threadably engaged with sleeve I20. This longitudinal move- If both sections were aeeeg'sso l3 mentis translated tocylinder 68cby$the means described and is in addition to thattranslated to cylinders 61 and 68 by shaft 91. Thus,.simultaneous rotation of shafts 9| 1 and 93 results in the'movement of cylinder 68 with respect to cylinder in which is necessary for thetuning of the oscillator. By reference to Fig. 3, it canbe- 93 turn simultaneously. When they so turn. simultanously, shaft 9| serves to-efiecttheentire.

physical length change required-in the plategrid' line and approximately three-fifths of that required in the cathode-grid line while shaft 93 serves to effect theremaining twoefifths change required inthe cathode: grid line. This differential movement of cylinder 68 may be. accomplished byproper choice ofthe ratio of gears 95. and 9? andof the ratio of the threaded sections of shafts 9i and sleeve IZEL It is recognized that end -conditions and lumped impedancesalong the lines being tuned may render the use of such an arbitrary ratio impossibleover a wide tuning range. For this reason, gear as may be moved longitudinally by pressing crank l til so as to disengage gear 96 and shaft 9! and so'as-to cause rotation of only shaft 93. This selectable independence of shaft'rotation permits correction of any detuning of the twosectionswhich may result from irregularities of the resonant sections. Calibration of the oscillator tuning is accomplished by means of a mechanical counter IEH driven by gears Hi2 and IE3 atthe end of shaft 9!. Since the rotational motion of shaft is translated into. longitudinal changes inthe resonant section lengths, the reading of mechanical counter lei will be an index of the electrical lengthof the resonant sections and the frequency of operation. While the immediately foregoing description has referred in particularto one end of the oscillator, it is to be understood fromthe essential symmetry of the oscillator that both ends are-tuned in a like manner, taking into account the fact. that.

themoving elements in the respective endsmove in opposite directions astheoscillator is tuned.

With furtherreference to Fig. 2, it should. be pointed outithat. the requirement that the electrical length of the cathodeegri'd line-in this rar ticularembodiment .be. approximately five half wavelengths makes it necessary to establish such electrical lengths for theseparate;portionsof the cathode-grid line at each endas to permitthe attainment of the desired electrical length for the line as a whole, It is the principles underlying the attainment of this-end, and the means of accomplishment thereof, which were omitted for convenience in the description of the oathode-grid line .in theidealized oscillator'of Fig. 1. In. addition to considerations of electrical length which. must be satisfied, certain feedback coup-ling driving, point impedance.considerations enter into the design of the cathode-grid line dimensions. Referring first to the radial cavity region immediately surrounding, the cathode and grid terminals of tube '5! in Fig. 2, which may be better understood from the detailed section of the oscillator shown in Fig. 2b, consider the loci of one pair of terminals forthis portion of the cathodegrid line to -lie in the one case along'the lip of ring HM. andfori'the other .terminalzalong..-thel immediately vadjacent..corneruof :tring 65.. .The.

other pair of terminalsfor this line. section. lie

at cathode 6i. and grid 60. of tube 5|,1i. e., atone end of the cathode-grid line asawholel The radial line section thus defined has an electrical length included betweenthe pair of terminals at cathode 64 and gridtil and the pair of terminals at parts HM and 65 which is dependent upon and approximately proportional. to theradiusof the cavity and which ismodified in. its effective value bythe existence of the cathode stem and cathode-gridinter-electrode capacitance within thetube envelope. line section is modified also by introducing any other changes in the dimensions or contour of the. bounding walls of the cavity. Thus the -capacitance between parts we and-baby the lipof part Hi4 increases the electrical length-ofthe radial line section. a desired increase in electrical length and-a desired terminal impedance for the radial'line section bya proper choice of dimensions for the lipof part [94. 7

Considering further the separate line sections composing the cathode-grid line, that portion of the line extending between terminals at the line midpoint and terminals at part Hi4 and the adjacent end-0f part 67 has an electricallength between one half and three quarters wavelength.

Therefore the electrical length of line required in'addition to complete the approximatelyfive quarter wavelengths for the one half" of thecathode-grid line is between one half and three quarters wavelength. The dimensions conveniently used for the radial line section permit this line section to have an electrical lengthbetween one half and three quarter wavelengths 'for all frequencies within'the frequency range of primary interest, although it'will be recognized that the electrical length of this radial cavity measured in half wavelengths will be substantially longer for the shortest wavelengths of operation than for the longest wavelengths since its dimension of the aforementionedline section terminating at one end at the line. midpoint does change with oscillator tuning, the degree of'change being such that the electrical lengthof this. line section measured in half wavelengthsis essentiallyconstant Withchange of operating frequency...

It is apparent therefore, that the twoportions of the cathodeegridlme will not include an electrical length of approximately five quarters wave-;

length for the whole .of the desired frequency range. ated cylinders Eli and B7? to providethe additional variable terminal impedance in series with the;

terminalimpedance between parts IE4 and, 65 required to represent the desired approximate resonance condition or desired electrical length for the line as a Whole for all frequencies of operation. In terms of impedance relationships, the impedance looking into the radial cavity from terminals at part ll iand part 65 is capacitive and exceeds in magnitude the inductive impedance seen'looking into the midsection from terminals at part ltd and at the adjacent end ofpart 61!. Therefore it is desired tomake the impedance looking toward part 68 from terminals at the end of part 6'5 and at part 65 inductive and to have a magnitude such as to produce the desired resonance condition. Because of the variation in magnitude of the impedance looking into the. radial cavity fromya relativelylow value" at the. high frequencyend'of the frequency ranget'o a' The effective length of this It is thus possible to provide It isthe function of part 68 and associhigher value at the low frequency end, the desired variation of the inductive impedance provided by part 68 will be in a similar sense, i. e., from a low value at the high frequency end of the frequency range to a higher value at the low frequency end. It will be seen that such a variation is consistent with the sense in which part 83 is moved by the tuning mechanism upon change of operating frequency.

Considering further the impedance relationship of the separate portions of the cathode-grid line, it will be recognized that the impedance looking into the terminals of any one of these line sections consists of a resistive as well as a reactive component, and that, while the reactive components of several line section impedances connected in series may be of such a sign and magnitude in the resonance condition as to substantially cancel one another in their sum, the resistive components will not so cancel. At the low frequency end of the frequency range the sum of the resistive components of the impedances looking into the radial cavity and into the line section containing part 68 will be higher than for the high frequency end of the frequency range, and will exceed at the low frequency end the characteristic impedance of the line section terminating at the midpoint. Therefore at the low frequency end of the frequency range the impedance looking from the midpoint toward the end of the cathode grid line assumes a capacitive component although the line is tuned to resonance. For frequencies near the high frequency end of the frequency range the sum of the resistive components of the line sections (radial cavity and line section including part 68) is small, and the impedance looking from the line midpoint is essentially resistive and of small magnitude, corresponding to the situation existing at the midpoint of a simple uniform resonant line an odd multiple of one half wavelength long and open at each end. The impedance of the cathode-grid line appearing in shunt with the feedback coupling slot is composed of resistive components of the impedance seen looking from the midpoint toward one end of the cathode-grid line, but differs in the magnitudes of the impedance components, in that the degree of coupling is small and the impedance components appearing in shunt with the slot generally exceed their counterparts seen from the line midpoint by many fold. Thus in this case, the shunt impedance across the slot is essentially resistive at the high frequency end of the frequency range, and at the low frequency end the shunt impedance consists of capacitive and resistive components. If the slot is tuned to near self-resonance, i. e., high self-impedance, at the high frequency end of the frequency range, then for the same adjustment of slot tuning the slot self-impedance will be inductive at the low frequency end. This inductive slot impedance in shunt with the capacitive component of the cathode-grid line impedance as seen from terminals across the slot affords a resultant high impedance across the slot as seen from the plate-grid line. Thus the degree of coupling and the phase relations between the plate-grid and cathode-grid lines are relatively constant over the frequency range, with the slot tuning fixed. Further correction of feedback magnitude and phase at any frequency in order to maximize the power output remains possible, if desired, by adjustment of the setting of plate 88 of Fig. 2a, together with readjustment of cathode-grid circuit tuning with respect to the plate-grid tuning.

Since tuned lines possess more than one resonant frequency, the separate resonant frequencies corresponding to several electrical lengths as measured in half wavelengths, the design of oscillators having tuned lines as circuit elements must be such as to insure that operation will take place at the desired frequency rather than at some undesired frequency corresponding to another mode of operation. In the case of this specific embodiment of this invention the electrical lengths of the plate-grid and cathode-grid lines are approximately three half and five half wavelengths respectively, for the desired frequency range. If these tuned lines were uniform in physical construction, i. e., constant characteristic impedance and negligible end effects, the undesired resonant frequencies would correspond to wavelengths of 30 and 15 centimeters for the plate-grid line, and wavelengths of 50, 25, 16.6 and 12.5 centimeters for the cathode-grid line, when the desired wavelength is 10 centimeters. For this idealized condition of line uniformity, it is seen that the only wavelength for which the push-pull condition of operation of both lines at the same wavelength is possible is 10 centimeters. However, in the practical embodiment of this invention the tuned lines are not uniform, but include substantial discontinuities in characteristic impedance and appreciable end effects. Therefore the undesired wavelengths of resonance corresponding to those named above will differ somewhat from these values, and the possibility arises that one of the undesired frequencies of resonance of the cathode-grid line may become the same as one of the undesired frequencies for the plate-grid line. In this case, oscillation at the undesired frequency requires only the additional condition that the phase relationships of the voltages appearing at the tube terminals correspond to either push-pull or to in-phase operation of both tuned lines. Of the various combinations possible, it may be seen that the ones most likely to permit undesired operation are, first, the combination of an electrical length of one wavelength for the plate-grid line with two wavelengths for the cathode-grid line yielding a frequency of operation lying between 2000 and 2500 megacycles per second (between 15 and 12.5 centimeters wavelength), second, the combination of one wavelength for the plate-grid line with one wavelength for the cathode-grid line yielding an operating Wavelength between 25 and 15 centimeters, and lastly, the combination of one half wavelength for the plate-grid line with one half wavelength for the cathode-grid line yielding an operating wavelength of roughly 30 centimeters. Of these combinations the first two represent operation with the electrical lengths of the lines as even multiple of one half wavelength. This corresponds to the existence of voltage loops at the line midpoints, and since the appearance of a voltage loop at the line midpoint will result in considerable coupling of R. F. energy out to the oscillator exterior by means of the D. C. leads, the power loss thus introduced prevents sustained oscillation at the corresponding undesired frequencies. On the other hand the last named possible combination permitting undesired oscillation corresponds to line lengths an odd multiple of one half wavelength and therefore the existence of this undesired frequency of oscillation will not be affected by the nature of the midpoint 17' impedances. However, the separation between the separate frequencies of resonance of the two lines in this case is such that undesired oscillations are not rendered possible by the senses and magnitudes in which the line lengths are changed by line discontinuities. Previously unmentioned have been annular conducting elements 58a, 59a,

and 6Ia, all best seen in Fig. 22). It will be recognized that all three of these elements serve to increase the capacitance across the plate-grid line and thus affect its electrical length. Such additional elements typify the practical changes which may be made in constructing the oscillator so as to cause it to operate successfully in a desired band of frequencies. Their location and dimensions are dictated by the requirements of the particular embodiment employed. In the embodiment of Fig. 2, for example, annular padding ring 6|a is employed at the tube end of the plate-grid line to help extend the frequency range of the oscillator up to 3400 megacycles per second. Ring Bla also serves, incidentally but usefully, to reinforce the mechanical spring action of slotted contact ring The permissible plate power dissipation of such an oscillator without auxiliary cooling would be considerably reduced. For this reason, a circulatory liquid'coolant system is employed. A small circulating pump (not shown) is connected by means of rubber hoses to hose connections 83 and I05 of Fig. 2. The input coolant enters the oscillator by way of hose connection I65 and travels down inner tube I66 into chamber I01. In contact with the walls of this chamber, the coolant receives the heat dissipated at anode 51 and the anode of the other tube and communicated to the chamber walls by the thermal contacts hereinbefore described. The heated coolant leaves the chamber by way of the annular space between tubes 8| and H16 and discharges out hose connection 83. It has been found that the insulation of the hoses and their water columns to the circulating pump is adequate to prevent the grounding of the B+ supply connected to hose connection 83. With reference to Fig. 2b, the separation between the inside element of movable dual cylinder 58 and cylinder 59 is, of course, a potential source of coolant leakage. For this reason, a packing gland consisting of a packing material I08 such as graphite flax packing, bevelled packing washer 199, and packing nut H6 is provided. The coolant seal thus constituted offers little friction, does not stick and easily withstands the pressures involved.

The transition from the ideal amplifier apparatus mentioned briefly in connection with Fig. 1 to a practical embodiment so parallels that of the oscillator that Fig. 2 may as well depict an embodiment of thisinvention employed as an amplifier. The distinction between oscillator and amplifier appears in Fig. 4 wherein the cutaway portions reveal the fact that the amplifier form lacks the slot coupling means comprising slot 63a and associated midpoint capacitance parts shown in Fig. 2a and Fig. but includes an inductive loop I20 disposed between cylindrical members 63 and H in the grid-cathode resonant section at the oscillator midpoint. Energy of the common resonant frequency of the gridcathode and grid-anode line sections introduced into the amplifier by means of input coupling I26 would be amplified by the apparatus for transference from the grid-anode section by means of output coupling loop 86.

The requirement inherent in an amplifier that it must be degenerative to the extent that selfoscillation is avoided may be satisfied in the amplifier embodiment of this invention, either by the proper selection of vacuum tube exciting means or by neutralization of anode-to-cathode capacitance by any of several known methods where such capacitance contributes to instability.

The extension of the field of usefulness of the triode oscillator into the microwave region means of construction according to the teachings of this invention results in several salient advantages. Since the triodes of the push-pull system are operated in a conventional negative grid manner, either plate circuit or grid circuit modulation may be employed in any of several ways; well known to the art. Operation of the oscillator may either be continuous with audio orvideo frequency modulation or it may be used for pulsed transmission. These features are, of course, those of typical triode operation at lowfrequencies and their extension into the micro-- wave spectrum with sizeable power output through push-pull operation is accomplished by the teachings herein disclosed.

Since certain further changes may be made in the foregoing constructions and different embodiments of the invention may be made without departing from the scope thereof, it is in-' tended that all matter shown in the accompanying drawings or set forth in the accompanyingspecification shall be interpreted as illustrative and not in a limiting sense. p The invention described-herein may be manufactured and'used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A high frequency apparatus comprising, three cylindrical elements all of different diameter concentrically disposed one within the other, a first and second triode vacuum tube fitted respectively to the ends of said cylindrical elements so as to form a grid-anode line section and a grid-cathode line section, means feed! ing energy to said grid-cathode section, and means coupling energy from one of said sections to an external load.

2. A high frequency apparatus comprising, three cylindrical elements all of different diam-- eter concentrically disposed one within the other,- a first and second triode vacuum tube fitted respectively to the ends of said cylindrical elements so as to form a grid-anode line section and a grid-cathode line section, said grid-anode and grid-cathode line sections possessing a copola-nar location of voltage minimum perpendicular to the axis of said cylindrical elements at the midpoint thereof, means feeding energy to said gridcathode section, and means coupling energy from one of said sections to an external load.

3. An oscillator assembly comprising, three cylindrical elements all of different diameter cone centricallydisposed one withintheother, a first and second triode vacuum tube fittedre'spectively to the ends of said cylindrical elements so as to form a grid-anode line section and a grid-cathode line section, means feeding energy from said grid-anode section to said grid-cathode section so as to cause and sustain oscillations, and means coupling energy from one of said sections to an external load.

4. A generator ofsinusoidal oscillations coma prising a first and second vacuum tube exciting means having annular electrode contacts, a plurality of cylindrical conducting members of diiferent diameters concentrically disposed one within the other adapted to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, 'in combination with said first and second vacuum tube exciting means two resonant line sections, means for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a 180 phase difference in the operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant sections to an external load.

5. A generator of sinusoidal oscillations comprising a first and second vacuum tube exciting means having annular electrode contacts, a plurality of cylindrical conducting members of different diameters concentrically disposed one within the other adapted to receive at "one end said first vacuum tube exciting means and at the other 'en'd said second'vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube means two resonant line sections each an odd integral number of half wavelengths in electrical length at the frequency of oscillation, means for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a 180 phase difference in operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant sections to an external load.

6. A generator of sinusoidal oscillations comprising a first and second vacuum tube exciting means having annular electrode contacts, a plurality of cylindrical conducting members of different diameters concentrically disposed one within the other adapted to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube exciting means a first resonant line section an odd integral number of half wavelengths in electrical length at the frequency of oscillation and a second resonant line section an odd integral number of half wavelengths in electrical length at said frequency and differing in electrical length from said first resonant section by an odd integral number of full wavelengths at said frequency, means for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a 180 phase difference in the operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant sections to an external load.

7. A generator of sinusoidal oscillations comprising a first and second vacuum tube exciting means having annular electrode contacts, a plurality of cylindrical .conducting members of different diameters concentrically disposed one within the other adapted "to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube exciting means a first resonant line section an odd integral number of half wavelengths in electrical length at the frequency of oscillation and a second resonant'line section an odd integral number of half wavelengths in electrical length at said frequency and differing in electrical length from said first resonant section'by an even a number of full wavelengths at said frequency, means for transferring energy from one of said resonant section to the other of said resonant sections in such a phase as to cause a phase difierence in the operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant section to an external load.

8. A generator of sinusoidal oscillations comprising a first and second vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a plurality of cylindrical conducting members of different diameter concentrically disposed one within the other adapted to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube exciting means two resonant line sections each with an electrical length such that the common physical trans verse midpoint plane of such resonant sections presents a location of minimum voltage variation at the frequency of oscillation, means located generally at such midpoint plane for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a 180 phase difference in the operation of said first and second vacuum tube exciting means, means located generally at such midpoint plane for transferring energy from one of said resonant sections to an external load, means located generally at such midpoint plane for providing connection from an external direct current power supply and means located generally at such midpoint for providing external direct current connection between the electrodes of said first and second vacuum tube exciting means.

9. A generator of high frequency sinusoidal oscillations tunable over a wide band of the frequency spectrum comprising a first and second vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a plurality of generally cylindrical conducting telescopic members of different diameters concentrically disposed one within the other adapted to receive at opposite ends said first and second vacuum tube exciting means in a face to face relationship in such a manner as to constitute, in combination with the plate-to-grid capacitances of said first and second vacuum tube exciting means a plate-grid adjustable length concentric transmission line resonant at the frequency of oscillation and characterized by a condition of oscillatory voltage minimum at .a point midway between said first and second vacuum tube exciting means, and in combination with the cathode and grid contact surfaces and interelectrode capacitances of said first and second vacuum tube exciting means, a cathode-grid adjustable length transmission line resonant at the frequency of oscillation and characterized by a similar midpoint oscillatory voltage minimum, means for simultaneously adjusting the physical length of said plate-grid line and said cathodegrid line so as to maintain a common resonant condition for tuning purposes, means for independently adjusting either of said lines so as to establish a common resonant condition, means for transferring energy from said plate-grid line to said cathode grid line in proper phase to result in a 180 difference in the phase of operation of said first and second vacuum tube exciting means, and means for transferring energy from said plate-grid line to an external load.

10. A generator of high frequency sinusoidal oscillations tunable over a wide band of the frequency spectrum comprising a first and second vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a plurality of cylindrical conducting members of adjustable length and of different diameters concentrically disposed one within the other adapted to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube exciting means two resonant line sections each an odd integral number of half wavelengths in electrical length at the frequency of oscillation determinable by adjustment of the physical length of said cylindrical conducting members, means for simultaneously adjusting the physical length of said cylindrical conducting members so as to maintain said electrical length relationship, means for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a 180 phase difference in the operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant sections to an external load.

11. A high-frequency apparatus comprising, a first and second vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a first cylindrical conducting member of such a diameter as to receive in one end the anode terminal of said first vacuum tube exciting means and in the opposite end the anode terminal of said second vacuum tube exciting means so as to position said tubes in a face to face relationship, a second cylindrical conducting member disposed concentrically with said first cylindrical member and of such a diameter as to contact at its ends the respective grid terminals of said tubes whereby a grid-anode resonant line section is formed, a third cylindrical conducting member disposed concentrically with said first and second cylindrical members and of such a diameter and construction as to contact at its opposite ends the respective cathode terminals of said first and second tubes to thereby form a grid-cathode resonant line section, said grid-anode and grid-cathode resonant line sections each being an odd integral number of onehalf wavelengths long at the frequency of operation, means feeding energy to said grid-cathode line section, and means for coupling energy from said grid-anode section to an external load.

12. A generator of sinusoidal oscillations comprising, a first and second vacuum tube exciting means each having projecting from it anode, grid,

and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a first cylindrical conducting member of such a diameter as to receive in one end the anode terminal of said first vacuum tube exciting means and in the opposite end the anode terminal of said second vacuum tube exciting means so as to position said tubes in a face-to-face relationship, a second cylindrical conducting member disposed concentrically with said first cylindrical member and of such a diameter as to contact at its ends the respective grid terminals of said tubes whereby a grid-anode resonant line section is formed, a third cylindrical conducting member disposed concentrically with said first and second cylindrical members and of such a diameter and construction as to contact at its opposite ends the respective cathode terminals of said first and second tubes to thereby form a grid-cathode resonant line section, said grid-anode and grid-cathode resonant line sections each being an odd integral number of one-half wavelengths long at the frequency of operation, coupling means transferring energy from said grid-anode line section to said gridcathode line section in such a phase as to cause phase difference in the operation of said first and second tubes, and means for coupling energy from said grid-anode section to an external load.

13. Apparatus as described in claim 12 wherein each of said cylindrical conducting members comprises at-least two concentric telescopically posiitoned cylindrical sections adapted for relative longitudinal movement for frequency adjustment.

14. Apparatus as described in claim 12 in which, said first cylindrical conducting member comprises a central cylindrical section and two dualend cylindrical sections arranged in telescopic relation therewith at the opposite ends thereof and adapted to engage the respective anode terminals of said first and second tubes, said second cylindrical conducting member comprises a central cylindrical section, two dual-end cylindrical sections arranged in telescopic relation therewith at opposite ends thereof, and an integral annular conducting ring fitted to the ends of each of said last-named dual-end cylindrical sections and adapted to contact the respective grid terminals of said first and second tubes, and said third cylindrical conducting member com rises a central cylindrical section, a pair of cylindrical end sections telescopically fitted thereinto at opposite ends thereof, and a pair of re-entrant cylindrical sections each integrally attached to a respective one of said last-named end sections, said reentrant sections constructed to contact the respective cathode terminals of said first and second tubes.

15. Apparatus as described in claim 12 together with a pair of concentric tubular conducting members located at the physical transverse midpoint of said cylindrical conducting members and perpendicular to the axis thereof, said pair of tubular members so arranged that its outer member is electrically secured to said first cylindrical conducting member to thereby provide a power connection to the anodes of said tubes, the inner member of said pair of tubular members and the annular space between it and. the out-er member of said pair of tubular members providing liquid coolant charge and discharge paths.

16. An amplifier of high-frequency energy comprising, a first and second "vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, a first cylindrical conducting member of such a diameter as to receive in one end the anode terminal of said first vacuum tube exciting means and in the opposite end the anode terminal of said second vacuum tube exciting means so as to position said tubes in a face-to-f-ace relationship, a second cylindrical conducting member disposed concentrically with said first cylindrical member and of such a diameter as to contact at its ends the respective grid terminals of said tubes whereby a grid-anode resonant line section is formed, a third cylindrical conducting member disposed concentrically with said first and second cylindrical members and of such a diameter and construction as to contact at its opposite ends the respective cathode terminals of said first and second tubes to thereby form a grid-cathode resonant line section, said grid-anode and gridcathode resonant line sections each being an odd integral number of one-half Wavelength-s long at the frequency of operation, inductive loop means for feeding energy to said grid-cathode section, and means for coupling energy from said grid-anode section to an external load.

17. Apparatus as described in claim 16 wherein each of said cylindrical conducting members comprises at least two concentric telescopically positioned cylindrical sections adapted for rela tive longitudinal movement for frequency adjustment.

18. Apparatus as described in claim 16 in which, said first cylindrical conducting member comprises a central cylindrical section and two dual-end cylindrical sections arranged in teles'cop-ic elation therewith at the opposite ends thereof and adapted to engage the respective an- Ode terminals of said first and second tube-s, said second cylindrical conducting member comprises a central cylindrical section, two dual-end cylindrical sections arranged in telescopic relation therewith at opposite ends thereof, and an integral "annular conducting ring fitted to the ends of each of said last-named dual-end cylindrical sections and adapted to contact the respective grid terminals of said first and second tubes, and said third cylindrical conducting member comprises a central cylindrical section, a pair of cylindrical end sections telescopically fitted thereinto at opposite ends thereof, and a pair of reen'trant cylindrical sec-tions each integrally attached to a respective one of said last-named end sections, said reentrant sections constructed to contact the respective cathode terminals of said first and second tubes.

19. Apparatus as described in claim 16 together with a pair of concentric tubular conducting members located at the physical transverse midpoint of saidcylindrical conducting members and perpendicular to the axis thereof, said pair of tubular members so arranged that its outer mem-- her is electrically secured to said first cylindrical conducting member to thereby provide a power connection to the anodes of said tubes, the inner member of said pair of tubular members and the annular space between it and the outer member of said pair of tubular members providing liquid coolant charge and discharge paths.

2o. A tunable generator of high-frequency energy which comprises, first and second concentric transmission line sections of adjustable length so concentrically disposed that the outer conductor of said first concentric line section forms the inner conductor of said second concentric line section, third and fourth concentric transmission line sections of adjustable length each so coaxially disposed with respect to said first and second concentric line sections that its outer conductor forms an extension of the outer conductor of said second con-centric line section at a respective end thereof, first and second radial transmission line sections each having connected to one outer circumferential terminal a respective end of said inner conductor of said second con-centric line section and to the other outer circumferential terminal one end of the inner conductor of a respective one of said third and fourth concentric line sections, first and second vacuum tube exciting means each having projecting from it anode, grid, and cathode terminals in the form of annular conducting elements and each supporting said elements concentrically in parallel planes perpendicular to its axis, said transmission line section-s being adapted to receive and position said first and second tubes in a face-to-face relationship coaxially with said concentric transmission line sections so as to form, in combination with the annular terminals and interelectrode capacitances of said first and second tubes 2. grid-anode resonant line section and a grid-cathode resonant line section, coupling means transferring energy from said gridanode section to said grid-cathode section in such a phase as to cause phase difference in the operation of said first and second tubes, means for coupling energy from said grid-anode section to an external load, and means for adjusting the lengths of said concentric transmission line sections so as to alter thereby the resonant frequency of said resonant line sections.

21. Apparatus as described in claim 20 in which, the inner conductors of said first and second concentric transmission line sections each comprise a central cylindrical member and two dual-end cylindrical members arranged in telescopic relation therewith at opposite ends thereof, said outer conductor of said second concentric transmission line section comprises a central cylindrical member and two end cylindrical ma- 'bers telescopically fitted thereinto at opposite ends thereof, said third and fourth concentric transmission line sections each coznxises concentric inner and outer conductors and an annular conducting member of adjustable coaxial position in contact with and disposed between last said inner and outer conductor, said two dual end cylindrical members of said inner conductor of' said first concentric line section being adapted to receive at opposite ends of last said inner condoctor said anode terminals of said first and second tubes, the inner circumferential terminals of said first and second radial transmission line sections corresponding to the outer circumferential terminals of said first and second radial transmission line sections connected as said to the inner conductor of said second concentric line section are adapted to contact said grid terminals of said first "and second tubes, and the other inner circumferential terminals of said first and second radial transmission line sections are adapted to contact said cathode terminals of said first and second tubes.

22. Apparatus as described in claim 20 together with, a pair of concentric tubular conducting memberslocated at the physical transversemidpoint of said first and second concentric transmission line sections and perpendicular to the axis thereof, said pair of tubular members so arranged that its outer member is electrically secured to said inner conductor of said first concentric line section to thereby provide a power connection to the anodes of said first and second tubes, the inner member of said pair of tubular members and the annular space between it and said outer member of said pair of tubular members providing liquid coolant paths for the charge into and discharge from the interior chamber of said inner conductor of said first concentric line section, and a grid-to-cathode biasing connection located at said physical transverse midpoint electrically secured to said inner conductor of said second concentric line section.

23. Apparatus as described in claim 20 in which, the electrical length of Said grid-anode resonant line section is three half wavelengths at the frequency of the ener y generated, and the electrical length of said grid-cathode resonant line section is five half wavelengths at said frequency.

24. Apparatus as described in claim 20 in which said coupling means transferring energy from said grid-anode resonant line section to said grid-cathode resonant line section comprises a transverse circumferential aperture in the inner conductor of said second concentric line section at the physical transverse midpoint thereof of a width equal to a fractional part of a wavelength at the frequency of the energy generated and a length equal to less than a half wavelength at said frequency having across it at its midpoint an adjustable capacitance for increasing the electrical length of said aperture to substantially a half wavelength at said frequency.

25. Apparatus as described in claim 20 in which said means for coupling energy from said grid-anode section to an external load comprises an inductive loop located between said inner and outer conductors of said first concentric transmission line section at the transverse physical midpoint thereof, said individual loop being of adjustable orientation with respect to the magnetic field of last said energy,

26. Apparatus as described in claim 20 in which said means for adjusting the lengths of said concentric transmission line sections comprises, means for adjusting said lengths simultaneously, and means for adjusting the length of said third and fourth concentric transmission lines independently of said first and second concentric transmission line sections.

27. Apparatus as described in claim 20 in which the inner conductor of said first concentric transmission line section comprises a central cylindrical member and two dual end cylindrical members arranged in telescopic relation therewith at opposite ends thereof, last said two dual end cylindrical members being adapted to receive at opposite ends of last said inner conductor said anode terminals of said first and sec- 0nd tubes so as to provide a coolant retaining seal between said dual end cylindrical members and said anodes, and the inner cylinder of said two dual-end cylindrical members each is provided at its free end with an annular coolant retaining seal which permits the axial movements of said two dual-end cylindrical members with respect to said central cylindrical member.

28. An ultra high frequency oscillator comprising a pair of electron discharge devices having control grids, a pair of resonant sections having a common boundary constituted in part by said grids, said devices having anodes disposed in one of said resonant sections and cathodes disposed in the other of said resonant sections, feedback means connected between said resonant sections, and means for adjusting the dimensions of said resonant sections to produce oscillations therein of a desired frequency.

29. A generator of sinusoidal oscillations comprising a first and second vacuum tube exciting means having annular electrode contacts, a plurality of cylindrical conducting members of different diameters concentrically disposed one within the other adapted to receive at one end said first vacuum tube exciting means and at the other end said second vacuum tube exciting means in such a manner as to constitute, in combination with said first and second vacuum tube exciting means a first resonant line section an odd integral number of half wavelengths in electrical length at the frequency of oscillation and a second resonant line section an equal odd integral number of half wavelengths in electrical length at said frequency, means for transferring energy from one of said resonant sections to the other of said resonant sections in such a phase as to cause a phase difierence in the operation of said first and second vacuum tube exciting means, and means for transferring energy from one of said resonant sections to an external load.

JOHN E. GIBSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,979,668 Boddie Nov. 6, 1934 2,159,782 Conklin May 23, 1939 2,169,305 Tunick Aug. 15, 1939 2,284,405 McArthur May 26, 1942 2,342,896 Salzberg Feb. 20, 1944 2,351,895 Allerding June 20, 1944 2,394,908 Gavin Feb. 12, 1946 2,408,355 Turner Sept. 24, 1946 2,411,424 Gurewitsch Nov. 19, 1946 2,412,992 Labin Dec. 24, 1946 2,416,315 Hartman Feb. 25, 1947 2,423,443 Fay July 8, 1947 2,423,444 West July 8, 1947 2,427,752 Stempel Sept. 23, 1947 

